Heavy fighting in the country's largest city has also sent thousands more refugees fleeing to neighboring countries, The New York Times reported. Adrian Edwards of the U.N. refugee agency said at least 6,000 Syrians have registered with the agency in Turkey this week, bringing the number there to more than 50,000.
In Aleppo, a commander with the Free Syrian Army identifying himself as Abu Mohammed told the Times the rebels had withdrawn from parts of the Salahuddin neighborhood to encircle the government troops.
"One day is ours, one day is theirs," he said. "We have very little capacities, but we have achieved much so far."
In demonstrations after Friday prayers, Syrian opposition members called on international supporters to supply them with antiaircraft weapons, the Times said.
British Foreign Minister William Hague said Friday the country will add to its support of the rebels, sending $7.8 million in "non-lethal" items, including medical supplies and communications equipment, The Daily Telegraph reported.
Mobile and satellite phones and radios to be given to the rebels represent "non-lethal practical assistance," said Hague, who stressed no military advice or weapons had been or would be given to the rebels.
Regime forces fired on rebel positions with jets, helicopters, artillery and tanks in the third day of a ground offensive, fighters and Syrian TV said.
The Syrian Arab News Agency reported heavy regime shelling and dozens of casualties in several other neighborhoods on the outskirts of the Chicago-size city.
SANA said Thursday the regime had "continued purging" Aleppo's neighborhoods, including Salahuddin, of what it called "mercenary terrorists" from Persian Gulf sheikdoms backing the rebels.
Opposition Free Syrian Army commanders said the Salahuddin withdrawal was tactical and a small force stayed behind to oppose any advance by regime forces.
The opposition fighters withdrew to the nearby Sukari district, "where they are preparing a counterattack against the [regime] army," Hossam Abu Mohammed, commander of the Dara al-Shahbaa Brigade, told al-Jazeera.
"A large number of civilians were killed, as were some 40 rebels," he said. "Forty buildings have been flattened."
The battle for the city has now raged for more than two weeks.
As Assad's forces moved on Aleppo, rebel forces retreating from parts of Syria's largest city said they controlled two border crossings to Turkey similar to enclaves that sustained Libyan civil war rebels.
The border crossings, staffed by rebels who check passports, enter names into computers and extend a welcome hand to "Free Syria," are part of a large swath of territory north of Aleppo that the rebels gained control of from regime troops in late July, The Wall Street Journal reported Friday.
Except for a single air base where loyalist soldiers are mostly surrounded by rebel fighters, the countryside stretching from Aleppo to the Turkish border about 30 miles away has been cleared of regime forces, the Journal said.
For fighters in need of food, fuel and weapons, the ability to freely cross the Turkish border and move between villages without fear of regime attack is a dramatic turnabout, the newspaper said.
Supply shipments now reach the Aleppo front line from the border in about 90 minutes, the Journal said.
By contrast, before rebels repulsed regime troops in an offensive that claimed much of the countryside the week of July 22, the trip took weeks, with smugglers sneaking food and weapons over treacherous regime-controlled routes, the newspaper said.
The opposition told the Journal it hoped the enclave would transform the fight in the 17-month-old uprising.